Editing Declination (section)

{{Short description|Astronomical coordinate analogous to latitude}}
{{Other uses}}
In [[astronomy]], '''declination''' (abbreviated '''dec'''; symbol '''''δ''''') is one of the two angles that locate a point on the [[celestial sphere]] in the [[equatorial coordinate system]], the other being [[hour angle]]. The declination angle is measured north (positive) or south (negative) of the [[celestial equator]], along the [[hour circle]] passing through the point in question.<ref>
{{cite book
 | last1 = U.S. Naval Observatory
 | first1=Nautical Almanac Office
 | editor = P. Kenneth Seidelmann
 | title = Explanatory Supplement to the Astronomical Almanac
 | publisher = University Science Books, Mill Valley, CA
 | date = 1992
 | isbn = 0-935702-68-7
 |page=724}}
</ref>

[[File:Ra and dec demo animation small.gif|right|thumb|350px|
[[Right ascension]] and '''declination''' as seen on the inside of the [[celestial sphere]]. The primary direction of the system is the [[equinox|vernal equinox]], the ascending node of the [[ecliptic]] (red) on the celestial equator (blue). Declination is measured northward or southward from the celestial equator, along the [[hour circle]] passing through the point in question.]]

The root of the word ''declination'' (Latin, ''declinatio'') means "a bending away" or "a bending down". It comes from the same root as the words ''incline'' ("bend forward") and ''recline'' ("bend backward").<ref>
{{cite book
|url=https://books.google.com/books?id=a6MRAAAAIAAJ
|title=A Complete and Universal English Dictionary
|first=James
|last=Barclay
|date=1799}}
</ref>

In some 18th and 19th century astronomical texts, declination is given as ''North Pole Distance'' (N.P.D.), which is equivalent to 90 – (declination). For instance an object marked as declination −5 would have an N.P.D. of 95, and a declination of −90 (the south celestial pole) would have an N.P.D. of 180.